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Biomedical subjects

C S Brown

Publications and source records attributed to C S Brown.

At least 55 records · Page 3Linked to original sources
PubMed1997

Spectral quality affects disease development of three pathogens on hydroponically grown plants.

Plants were grown under light-emitting diode (LED) arrays with various spectra to determine the effects of light quality on the development of diseases caused by tomato mosaic virus (ToMV) on pepper (Capsicum annuum L.), powdery mildew [Sphaerotheca fuliginea (Schlectend:Fr.) Pollaci] on cucumber (Cucumis sativus L.), and bacterial wilt (Pseudomonas solanacearum Smith) on tomato (Lycopersicon esculentum Mill.). One LED (660) array supplied 99% red light at 660 nm (25 nm bandwidth at half-peak height) and 1% far-red light between 700 to 800 nm. A second LED (660/735) array supplied 83% red light at 660 nm and 17% far-red light at 735 nm (25 nm bandwidth at half-peak height). A third LED (660/BF) array supplied 98% red light at 660 nm, 1% blue light (BF) between 350 to 550 nm, and 1% far-red light between 700 to 800 nm. Control plants were grown under broad-spectrum metal halide (MH) lamps. Plants were grown at a mean photon flux (300 to 800 nm) of 330 micromoles m-2 s-1 under a 12-h day/night photoperiod. Spectral quality affected each pathosystem differently. In the ToMV/pepper pathosystem, disease symptoms developed slower and were less severe in plants grown under light sources that contained blue and UV-A wavelengths (MH and 660/BF treatments) compared to plants grown under light sources that lacked blue and UV-A wavelengths (660 and 660/735 LED arrays). In contrast, the number of colonies per leaf was highest and the mean colony diameters of S. fuliginea on cucumber plants were largest on leaves grown under the MH lamp (highest amount of blue and UV-A light) and least on leaves grown under the 660 LED array (no blue or UV-A light). The addition of far-red irradiation to the primary light source in the 660/735 LED array increased the colony counts per leaf in the S. fuliginea/cucumber pathosystem compared to the red-only (660) LED array. In the P. solanacearum/tomato pathosystem, disease symptoms were less severe in plants grown under the 660 LED array, but the effects of spectral quality on disease development when other wavelengths were included in the light source (MH-, 660/BF-, and 660/735-grown plants) were equivocal. These results demonstrate that spectral quality may be useful as a component of an integrated pest management program for future space-based controlled ecological life support systems.

Biomass↗
PubMed1997

Potato tuber formation in the spaceflight environment.

Five potato (Solanum tuberosum L.) leaf cuttings were flown on STS-73 in late October, 1995 as part of the 16-day USML-2 mission. Preflight studies were conducted to study tuber growth, determine carbohydrate concentrations, and examine the developing starch grains within the tuber. In these tests, tubers attained a fresh weight of 1.4 g tuber-1 after 13 days. Tuber fresh mass was significantly correlated to tuber diameter. Greater than 60% of the tuber dry mass was starch and the starch grains varied in size from 2 to 40 micrometers in the long axis. For the flight experiment, cuttings were obtained from 7-week-old Norland potato plants, kept at 5 degrees C for 12 h then planted into arcillite in the ASTROCULTURE(TM) flight hardware. The flight package was loaded on-board the orbiter 22 h prior to launch. During the mission, the flight hardware maintained an environment around the cuttings of 22 +/- 2 degrees C, 81 +/- 7% RH, and a 12-h photoperiod using red and blue light-emitting diodes at a photosynthetic photon flux of 150 micromol m-2 s-1. CO2 concentration exceeded 4000 ppm during the dark period and was controlled during the light period to approximately 400 ppm. Video downlinking of images of the plants and CO2 exchange data during the flight demonstrated plant vitality for the first 12 days of the mission followed by senescence of the leaves. The flight package was received 4 h after landing at the Kennedy Space Center and postflight processing of the samples was completed within 3 h. Four out of the five space-grown cuttings produced tubers that were similar in appearance and dimension to the ground control tubers. This is an important finding if potatoes are to be used as part of a bioregenerative life support system for long-term space exploration.

Biomass↗
PubMed1996

Optimization of moisture content for wheat seedling germination in a cellulose acetate medium for a space flight experiment.

The Porous Tube Plant Nutrient Delivery System (PTPNDS), a hydrophilic, microporous ceramic tube hydroponic system designed for microgravity, will be tested in a middeck locker of the Space Shuttle. The flight experiment will focus on hardware operation and assess its ability to support seed germination and early seedling growth in microgravity. The water controlling system of the PTPNDS hardware has been successfully tested during the parabolic flight of the KC-135. One challenge to the development of the space flight experiment was to devise a method of holding seeds to the cylindrical porous tube. The seed-holder must provide water and air to the seed, absorb water from the porous tube, withstand sterilization, provide a clear path for shoots and roots to emerge, and be composed of flight qualified materials. In preparation for the flight experiment, a wheat seed-holder has been designed that utilizes a cellulose acetate plug to facilitate imbibition and to hold the wheat seeds in contact with the porous tube in the correct orientation during the vibration of launch and the microgravity environment of orbit. Germination and growth studies with wheat at a range of temperatures showed that optimal moisture was 78% (by weight) in the cellulose acetate seed holders. These and other design considerations are discussed.

Cellulose↗
PubMed1996

IgG subclass response to human parvovirus B19 infection.

BACKGROUND: IgG antibodies are essential to immunity against human parvovirus B19 and can neutralize infection both in bone marrow cell cultures infected in vitro and in chronically infected immunosuppressed individuals. OBJECTIVES: To assess the levels and response kinetics of IgG subclasses towards individual structural proteins of human parvovirus B19. STUDY DESIGN: Subclasses of IgG for capsid proteins VP1 or VP2 were quantified by EIA using monoclonal antibodies in 30 acutely infected and 30 convalescent patients, as well as in 32 remotely infected and 20 non-infected controls. RESULTS: In all groups of seropositive individuals the predominant subclass for either structural protein was IgG1. Subclass IgG3 was associated with acute infection. By contrast, IgG4 appeared months after infection, and occurred specifically towards VP1. The ratio of VP1-specific subclasses IgG3 and IgG4 provided a diagnostic test for recent infection with a specificity of 98% and a sensitivity of 97%. CONCLUSIONS: Comparative measurement of VP1-specific IgG3 and IgG4 is useful in diagnosis. The IgG4 results point to long-term expression of immunologically active VP1 and to T-cell help of T(h)2 type for B-cells recognizing VP1.

Journal Article↗
PubMed1996

Clinorotation affects morphology and ethylene production in soybean seedlings.

The microgravity environment of spaceflight influences growth, morphology and metabolism in etiolated germinating soybean. To determine if clinorotation will similarly impact these processes, we conducted ground-based studies in conjunction with two space experiment opportunities. Soybean (Glycine max [L.] Merr.) seeds were planted within BRIC (Biological Research In Canister) canisters and grown for seven days at 20 degrees C under clinorotation (1 rpm) conditions or in a stationary upright mode. Gas samples were taken daily and plants were harvested after seven days for measurement of growth and morphology. Compared to the stationary upright controls, plants exposed to clinorotation exhibited increased root length (125% greater) and fresh weight (42% greater), whereas shoot length and fresh weight decreased by 33% and 16% respectively. Plants grown under clinorotation produced twice as much ethylene as the stationary controls. Seedlings treated with triiodo benzoic acid (TIBA), an auxin transport inhibitor, under clinorotation produced 50% less ethylene than the untreated control subjected to the same gravity treatment, whereas a treatment with 2,4-D increased ethylene by five-fold in the clinorotated plants. These data suggest that slow clinorotation influences biomass partitioning and ethylene production in etiolated soybean plants.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

Growth and photosynthetic responses of wheat plants grown in space.

Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment.

Carotenoids↗
PubMed1996

Infrared light-emitting diode radiation causes gravitropic and morphological effects in dark-grown oat seedlings.

Oat (Avena sativa cv Seger) seedlings were irradiated with IR light-emitting diode (LED) radiation passed through a visible-light-blocking filter. Infrared LED irradiated seedlings exhibited differences in growth and gravitropic response when compared to seedlings grown in darkness at the same temperature. Thus, the oat seedlings in this study were able to detect IR LED radiation. These findings call into question the use of IR LED as a safe-light for some photosensitive plant response experiments. These findings also expand the defined range of wavelengths involved in radiation-gravity (light-gravity) interactions to include wavelengths in the IR region of the spectrum.

Avena↗
PubMed1996

Nefazodone: its place among antidepressants.

OBJECTIVE: To review the pharmacology, pharmacokinetics, efficacy, adverse effects, and drug interactions of nefazodone as well as to determine its place among currently available antidepressants. DATA SOURCES: A search of European and American literature using EMBASE and MEDLINE was completed. Nefazodone was the search term. DATA SYNTHESIS: Nefazodone is an antidepressant that blocks serotonin type 2 (5-HT2) receptors in addition to inhibiting the reuptake of serotonin and norepinephrine. In double-blind, placebo-controlled studies, nefazodone demonstrates antidepressant activity at dosages ranging from 400 to 600 mg/d. Sedation, dry mouth, nausea, and dizziness are the more common adverse effects of nefazodone. Nefazodone, an analog of trazodone, has not been associated with priapism at this time, and may have fewer sexual adverse effects than other antidepressants. More studies are needed to determine the potential role of nefazodone in treating anxiety, pain, and premenstrual syndrome. STUDY SELECTION: Only double-blind, placebo-controlled studies designed to establish the efficacy of nefazodone as an antidepressant were reviewed. CONCLUSIONS: Based on placebo-controlled, double-blind, comparative trials, nefazodone demonstrates greater efficacy than placebo, and equivalent efficacy to imipramine. Somnolence, dry mouth, nausea, dizziness, and constipation are the most common adverse effects. Nefazodone appears to have a milder adverse effect profile than the tricyclic antidepressants, causes fewer sexual dysfunctions than the serotonin selective reuptake inhibitors, and may cause less dizziness than trazodone. Nefazodone at dosages of at least 300 mg/d provides another option for the treatment of depression.

Antidepressive Agents, Second-Generation↗
PubMed1995

A novel series of amphiphilic imidazolinium compounds for in vitro and in vivo gene delivery.

We have developed three catioinic amphiphiles based on the structure 1-[2-(acyloxy)ethyl]-2-alkyl(alkenyl)-3-(2-hydroxyethyl)imidazolinium chloride. Although these three compounds differ only in the structure of the hydrophobic acyl chains, they differ greatly in their ability to mediate in vivo and in vitro gene delivery. Moreover, in vitro efficiency is not predictive of in vivo efficiency. The myristoyl form is the most effective compound in vitro, and the oleoyl form is the most effective compound in vivo. The compounds readily form suspensions in aqueous media, both in the pure form and as mixtures with either cholesterol or dioleoylphosphatidylethanolamine. These suspensions can be sonicated to produce smaller particles. Particle size, electron microscopy, and the ability to capture glucose suggest that these lipids form liposomes on suspension in aqueous media. When mixed with plasmid DNA, the lipid particles appear to fuse and form larger particles. Fusion is maximal at the critical DNA:lipid ratio where extensive aggregation and precipitation are observed. Therefore, these compounds behave similarly to other cationic liposome-forming lipids upon interaction with DNA.

Animals↗
PubMed1995

Glutamate-mediated excitotoxic death of cultured striatal neurons is mediated by non-NMDA receptors.

Considerable interest has focused on the role of glutamate-mediated excitotoxicity in neurodegenerative disorders of the basal ganglia. The in vitro data on the receptor mechanisms involved in this process, however, have been inconclusive. Some studies have indicated that excitotoxins acting at NMDA receptors kill striatal neurons and others have indicated that NMDA receptor-mediated excitotoxic death of striatal neurons is minimal in the absence of cortex. In the present study, we used a pharmacological approach to carefully reexamine this issue in 2-week-old cultures of striatal neurons dissociated from E17 rat embryos. The sensitivity of these neurons to glutamate agonists and antagonists was determined by monitoring cell loss in identified regions of the growth dishes. We found that glutamate killed striatal neurons with an EC50 of 100 microM. This loss was not mediated by NMDA receptors, since it was not reduced by the NMDA receptor antagonist APV (0.1-1.0 mM). Consistent with this result, up to 50 mM NMDA receptor-specific excitotoxin quinolinic acid (QA) did not affect neuronal survival. Depolarizing the QA-exposed neurons with 35 mM potassium chloride to enhance NMDA receptor activation by QA also did not produce neuron loss. The metabotropic glutamate receptor antagonist AP3 (500 microM) also had no effect on the striatal neuron loss produced by 100 microM glutamate. In contrast, the non-NMDA antagonist GYKI 52466 (100 microM) did block the excitotoxic effect of glutamate (100 microM). Specific AMPA and KA receptor agonists and the non-NMDA antagonist GYKI 52466 revealed that the non-NMDA receptor-mediated excitotoxic effect of glutamate was mediated by KA receptors. These results suggest that cultured striatal neurons are directly vulnerable to non-NMDA glutamate agonists, but not to NMDA and metabotropic glutamate agonists. Thus, non-NMDA receptors may play a greater role in the excitotoxic death of striatal neurons in disease and experimental animal models than previously realized.

Animals↗
PubMed1995

Protein expression in Arabidopsis thaliana after chronic clinorotation.

Soluble protein expression in Arabidopsis thaliana L. (Heynh.) leaf and stem tissue was examined after chronic clinorotation. Seeds of Arabidopsis were germinated and plants grown to maturity on horizontal or vertical slow-rotating clinostats (1 rpm) or in stationary vertical control units. Total soluble proteins and in vivo-labeled soluble proteins isolated from these plants were analyzed by two-dimensional SDS PAGE and subsequent fluorography. Visual and computer analysis of the resulting protein patterns showed no significant differences in either total protein expression or in active protein synthesis between horizontal clinorotation and vertical controls in the Arabidopsis leaf and stem tissue. These results show chronic clinorotation does not cause gross changes in protein expression in Arabidopsis.

Arabidopsis↗
PubMed1995

Accurate serodiagnosis of B19 parvovirus infections by measurement of IgG avidity.

In an attempt to improve diagnosis of illnesses caused by parvovirus B19 and to discriminate primary from secondary infections, a protein-denaturing assay for avidity of parvovirus-specific IgG antibodies was developed. The assay used three types of purified recombinant antigens: a fusion protein containing the unique portion of the structural protein VP1, entire capsids made up of the major structural protein VP2 alone, or VP2 plus VP1. The avidity assays were evaluated by testing sequential acute-phase serum samples from 61 well-characterized patients (34 were followed > or = 6 months), sera from 38 controls with evidence of past infection, and sera from 388 seropositive patients studied for evidence of B19 infection during an epidemic. Parvovirus capsids consisting of VP2 alone yielded unusual IgG avidity and IgG antibody responses. Three different IgG avidity assays based on VP1 protein antigens were highly sensitive and specific and were considered suitable for identification of recent primary infections by human parvovirus B19.

Antibodies, Viral↗
PubMed1995

Epitope type-specific IgG responses to capsid proteins VP1 and VP2 of human parvovirus B19.

Temporal reactivities of IgG towards native and linear antigenic determinants in assembled capsids or isolated structural proteins of human parvovirus B19 were measured by an epitope type-specific IgG EIA and by immunoblots. Antigens used were baculovirus-expressed B19 capsids composed of the proteins VP1 and VP2 in their native proportion, VP2 alone, or a prokaryotic VP1 fusion protein. Follow-up sera after primary infection were compared with samples from previously infected persons. The IgG responses during acute and early convalescence phases were directed towards both conformational and linear epitopes of VP2. The antibodies against the linear VP2 epitopes disappeared abruptly within 6 months; however, the conformational VP2 antibodies persisted. The epitope type-specific IgG reactivity of VP1 was strikingly different from that of VP2. On the basis of these results, two novel tests were developed for patient diagnosis. Both tests are suitable for verifying the time of human parvovirus infection.

Antibodies, Viral↗
PubMed1995

Microgravity and clinorotation cause redistribution of free calcium in sweet clover columella cells.

In higher plants, calcium redistribution is believed to be crucial for the root to respond to a change in the direction of the gravity vector. To test the effects of clinorotation and microgravity on calcium localization in higher plant roots, sweet clover (Melilotus alba L.) seedlings were germinated and grown for two days on a slow rotating clinostat or in microgravity on the US Space Shuttle flight STS-60. Subsequently, the tissue was treated with a fixative containing antimonate (a calcium precipitating agent) during clinorotation or in microgravity and processed for electron microscopy. In root columella cells of clinorotated plants, antimonate precipitates were localized adjacent to the cell wall in a unilateral manner. Columella cells exposed to microgravity were characterized by precipitates mostly located adjacent to the proximal and lateral cell wall. In all treatments some punctate precipitates were associated with vacuoles, amyloplasts, mitochondria, and euchromatin of the nucleus. A quantitative study revealed a decreased number of precipitates associated with the nucleus and the amyloplasts in columella cells exposed to microgravity as compared to ground controls. These data suggest that roots perceive a change in the gravitational field, as produced by clinorotation or space flights, and respond respectively differently by a redistribution of free calcium.

Antimony↗
PubMed1995

Root-shoot interaction in the greening of wheat seedlings grown under red light.

Wheat seedlings grown with roots exposed to constant red light (300-500 micromoles m-2 s-1) did not accumulate chlorophyll in the leaves. In contrast, seedlings grown with their roots shielded from light accumulated chlorophylls. Chlorophyll biosynthesis could be induced in red-light-grown chlorophyll-deficient yellow plants by either reducing the red-light intensity at the root surface to 100 micromoles m-1 s-1 or supplementing with 6% blue light. The inhibition of chlorophyll biosynthesis was due to impairment of the Mg-chelatase enzyme working at the origin of the Mg-tetrapyrrole pathway. The root-perceived photomorphogenic inhibition of shoot greening demonstrates root-shoot interaction in the greening process.

Chlorophyll↗
PubMed1995

Clinorotation affects soybean seedling morphology.

Although spaceflight does not appear to significantly affect seed germination, it can influence subsequent plant growth. On STS-3 and SL-2, decreased growth (measured as plant length, fresh weight and dry weight) was noted for pine, oat and mung bean. In the CHROMEX-01 and -02 experiments with Haplopappus and in the CHROMEX-03 experiment with Arabidopsis, enhanced root growth was noted in the space-grown plants. In the CHROMEX-04 experiment with wheat, both leaf fresh weight and leaf area were diminished in the space-grown plants but there was no difference in total plant height (CS Brown, HG Levine, and AD Krikorian, unpublished data). These data suggest that microgravity impacts growth by whole plant partitioning of assimilates. The objective of the present study was to determine the influence of clinorotation on the growth and morphology of soybean seedlings grown in the BRIC (Biological Research In Canister) flight hardware. This experiment provided baseline data for a spaceflight experiment (BRIC-03) flown on STS-63 (Feb. 3-11, 1995).

Gravitation↗